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Bathymetry, substrate and circulation in Westcott Bay, San Juan Islands, Washington, Data catolgue

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Metadata:


Identification_Information:
Citation:
Citation_Information:
Originator:
Grossman. E.E., Stevens, A., Curran, C., Smith, C., and Schwartz, A.
Publication_Date: 2007
Title:
Bathymetry, substrate and circulation in Westcott Bay, San Juan Islands, Washington, Data catolgue
Geospatial_Data_Presentation_Form: tabular digital data
Larger_Work_Citation:
Citation_Information:
Originator:
Grossman. E.E., Stevens, A., Curran, C., Smith, C., and Schwartz, A.
Publication_Date: 2007
Title:
Bathymetry, substrate and circulation in Westcott Bay, San Juan Islands, Washington
Series_Information:
Series_Name: Open-File Report
Issue_Identification: 2007-1305
Publication_Information:
Publication_Place: Menlo Park, CA
Publisher: U.S. Geological Survey, Coastal and Marine Geology Program
Online_Linkage: <http://pubs.usgs.gov/of/2007/1305/>
Description:
Abstract:
Nearshore bathymetry, substrate type, and circulation patterns in Westcott Bay, San Juan Islands, Washington, were mapped using two acoustic sonar systems, video and direct sampling of seafloor sediments producing these data.
Purpose:
The goal of the project was to characterize nearshore habitat and conditions influencing eelgrass (Z. marina) where extensive loss has occurred since 1995. A principal hypothesis for the loss of eelgrass is a recent decrease in light availability for eelgrass growth due to increase in turbidity associated with either an increase in fine sedimentation or biological productivity within the bay.
Supplemental_Information:
To explore sources for this fine sediment and turbidity, a dual-frequency Biosonics sonar operating at 200 and 430 kHz was used to map seafloor depth, morphology and vegetation along 69 linear kilometers of the bay. The higher frequency 430 kHz system also provided information on particulate concentrations in the water column. A boat-mounted 600 kHz RDI Acoustic Doppler Current Profiler (ADCP) was used to map current velocity and direction and water column backscatter intensity along another 29 km, with select measurements made to characterize variations in circulation with tides. An underwater video camera was deployed to ground-truth acoustic data. Seventy one sediment samples were collected to quantify sediment grain size distributions across Westcott Bay. Sediment samples were analyzed for grain size at the Western Coastal and Marine Geology Team sediment laboratory in Menlo Park, CA.
Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20070531
Ending_Date: 20070605
Currentness_Reference: ground condition
Status:
Progress: Complete
Maintenance_and_Update_Frequency: None planned
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -123.17290
East_Bounding_Coordinate: -123.13793
North_Bounding_Coordinate: 48.60642
South_Bounding_Coordinate: 48.58775
Keywords:
Theme:
Theme_Keyword_Thesaurus: General
Theme_Keyword: U.S. Geological Survey
Theme_Keyword: USGS
Theme_Keyword: Coastal and Marine Geology Program
Theme_Keyword: CMGP
Theme_Keyword: bathymetry
Theme_Keyword: substrate
Theme_Keyword: circulation
Theme_Keyword: sediment
Theme_Keyword: current
Theme_Keyword: oceans and estuaries
Theme:
Theme_Keyword_Thesaurus: ISO 19115 Topic Category
Theme_Keyword: geoscientificinformation
Theme_Keyword: location
Theme_Keyword: oceans
Theme_Keyword: inlandWaters
Theme_Keyword: elevation
Theme:
Theme_Keyword_Thesaurus: Global Change Master Directory (GCMD)
Theme_Keyword: Earth Science > Oceans > Bathymetry/Seafloor Topography
Theme_Keyword: Earth Science > Oceans > Coastal Processes
Theme_Keyword: Earth Science > Oceans > Marine Sediments
Theme_Keyword: Earth Science > Oceans > Ocean Circulation
Theme_Keyword: Instruments > Grab Samplers
Place:
Place_Keyword_Thesaurus: General
Place_Keyword: WA
Place_Keyword: USA
Place:
Place_Keyword_Thesaurus: Geographic Names Information System (GNIS)
Place_Keyword: Wescott Bay
Place_Keyword: San Juan Islands
Place_Keyword: Washington
Access_Constraints: None
Use_Constraints:
Public domain data from the U.S. government is freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey (USGS) as the source of this information.
Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Eric Grossman
Contact_Organization: U.S. Geological Survey, Coastal and Marine Geology
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical address
Address: 400 Natural Bridges Dr
City: Santa Cruz
State_or_Province: CA
Postal_Code: 95060-5792
Country: USA
Contact_Voice_Telephone: (831) 427-4725
Contact_Facsimile_Telephone: (831) 427-4748
Contact_Electronic_Mail_Address: egrossman@usgs.gov
Browse_Graphic:
Browse_Graphic_File_Name:
<http://walrus.wr.usgs.gov/infobank/b/b607ps/html/b-6-07-ps.meta.html>
Browse_Graphic_File_Description: Index map of field activity B-6-07-PS.
Browse_Graphic_File_Type: GIF
Cross_Reference:
Citation_Information:
Originator: U.S. Geological Survey, Coastal and Marine Geology Program
Publication_Date: 2007
Title: InfoBank
Online_Linkage:
<http://walrus.wr.usgs.gov/infobank/b/b607ps/html/b-6-07-ps.meta.html>


Data_Quality_Information:
Logical_Consistency_Report:
A) Bathymetric mapping

The root mean square (RMS) error of the processed surface elevation values were derived from survey line crossings. Line crossings did not always capture the same point on the seafloor (because of GPS accuracy, navigation, currents, and timing of data recording). Therefore, variability in elevation values at crossings is likely in part derived from variability in the bathymetry of the seafloor where line crossings spanned 0.5 to 2 m apart in the horizontal.

Because there can be significant natural variability in depth/elevation across 0.5 to 2.0 m of the seafloor, the vertical error of the survey was determined from analysis of three classes of elevation values at line crossings:

1) values within 2 m of each other from all areas of Westcott Bay including vegetated, rocky and smooth areas (RMS=9.8 cm, n=66)

2) values within 2 m of each other from the smooth area between Bell Point and the head of Westcott Bay (RMS=3.6 cm, n=22)

3) values within 0.5 m of each other within the smooth area between Bell Point and the head of Westcott Bay (RMS=2.6 cm, n=6)

The overall error for the entire survey is therefore 9.8 cm, although particular areas, especially characterized by low relief likely have much smaller errors.

B) Sediment Samples for Grain Size Analyses

Triplicate samples were collected at sites WBN and BP for error analyses.

Analyses of triplicate samples collected at stations WBN and BP show that inter-station variability around the mean grain size ranged ±0.054 mm. The results were then gridded across the bathymetric surface with a nearneighbor gridding algorithm averaging between the three nearest points.

Video of the seafloor was collected along several principal transects in the western and central portions of Westcott Bay to ground-truth the sonar data.

C) Nearshore Currents

Select transects at the mouth of Westcott Bay, Bell Point and immediately east of the Westcott Sea Farm were repeated ~2-3 times under flooding and ebbing tides.

Completeness_Report:
A) Bathymetric mapping

Sixty-nine (69) kilometers of acoustic bathymetry/substrate data were collected with a dual-frequency (200 and 430 kHz) Biosonics system along 142 transects in Westcott and Garrison Bays between 5/31/07 and 6/2/07. The Biosonics sonar generates a 6-degree cone of sound, which translates into a footprint on the seafloor ranging 0.2 to 0.8 m for the water depths surveyed (2 - 8 m). Ship speed generally ranged 4.0-4.5 kts and data were merged with GPS positions at 1 Hz. Resulting data therefore represent 0.2-0.8 m pixels on the seafloor spaced approximately 1-2 m apart along track lines. Track lines were spaced 25 m apart. Twenty (20) km of topographic elevation data were also collected across the upper intertidal region by walking the shoreface with a portable Trimble 4700 RTK-DGPS receiver. This receiver utilized a Trimble Zepher Antenna and Pacific Crest radio receiver to obtain real time position corrections from a base station operating a Trimble 4400 receiver and L1/L2 antenna with a Pacific Crest 35 Watt radio transmitter. Elevation data over emergent beaches and tide flats collected by walking are 2-3 times denser as a result of survey speeds ranging 0.5-1.0 kts.

B) Sediment Samples for Grain Size Analyses

Sediment samples were collected using a van veen grab sampler at 71 stations on a 200-250 m grid to characterize grain size distribution throughout Westcott Bay and sources of fine material for suspension and transport.

The shallow stratigraphy was well-preserved in the sediment grabs so that a 1-3 cm thick aerated surface layer could be observed at most stations dominated by fines.

In the field, a sub-sample of the uppermost 1-3 cm of each grab was collected and placed into storage bags, labeled, logged, and frozen. Several 10-cm push cores were also collected.

In the laboratory, sediment samples were split for grain size and carbon analyses and later archived at the Western Coastal and Marine Geology Team sediment laboratory in Menlo Park, CA. Samples were disaggregated and sieved through 2000 and 62 micron screens to separate gravel, sands and mud after the organic component was removed by treatment with hydrogen peroxide. Sediment grain size of sands was determined using the settling methods and principles of Stokes Law on the USGS 3-m long settling tubes. The fine fraction (silts and clays) were analyzed on a Coulter 230 Laser Particle Analyzer. Three samples had less than 3% intermediate fraction and were analyzed on the Coulter. Single sample runs were made on the tubes, while results from the laser particle analyzer are averages of triplicates with standard deviations around the mean ranging 18 to 24 microns due to instrument errors.

C) Nearshore Currents

Current velocity, direction and backscatter amplitude were collected along 65 transects in Westcott Bay with a 600 kHz RDI ADCP (Acoustic Doppler Current Profiler) and recorded with WinRiver software. ADCP were recorded with GPS position at 1 hz with a ship speed of 2.0-2.5 kts, so raw ADCP data cover a lateral distance of 1.00 to 1.25 m.

Lineage:
Process_Step:
Process_Description:
A) Bathymetric mapping

The combined bathymetric and topographic data were merged to create a digital elevation model representing the surface topography of Westcott Bay. This surface is referenced to the WGS 84 datum in the UTM Zone 10 North projection with a horizontal accuracy of 2.3 cm. Elevations are referenced to NAVD88 with an estimated vertical accuracy ranging 2.6-9.8 cm. This includes error from the RTK-DGPS and Biosonics sonar, and errors introduced in data processing.

Process_Date: 2007
Process_Step:
Process_Description:
B) Sediment Samples for Grain Size Analyses

Results from the tubes and laser particle analyzer were merged using standard USGS methods found in the USGS particle analysis program pcSedSize.

Process_Date: 2007

Process_Step:
Process_Description:
C) Nearshore Currents

The raw ADCP data were vertically binned at 0.25 m and include a blanking distance of 0.25 m (no data in uppermost 0.25 m below the transducer). The RDI ADCP is accurate to within 0.25% of boat + water velocity, resulting in an error for our velocity data of 0.25 to 0.45 cm/s based on our survey speed of 2 kts and measured velocities ranging 0 to 1.5 m/s.

Process_Date: 2007


Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: Point


Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Geographic:
Latitude_Resolution: 0.00001
Longitude_Resolution: 0.00001
Geographic_Coordinate_Units: Decimal degrees
Geodetic_Model:
Horizontal_Datum_Name: North American Datum of 1983
Ellipsoid_Name: Geodetic Reference System 80
Semi-major_Axis: 6378137.000000
Denominator_of_Flattening_Ratio: 298.257222
Vertical_Coordinate_System_Definition:
Altitude_System_Definition:
Altitude_Datum_Name: North American Vertical Datum of 1988
Altitude_Resolution: 0.1
Altitude_Distance_Units: meters
Altitude_Encoding_Method:
Explicit elevation coordinate included with horizontal coordinates
Depth_System_Definition:
Depth_Datum_Name: local surface
Depth_Resolution: 0.1
Depth_Distance_Units: meters
Depth_Encoding_Method: Explicit depth coordinate included with horizontal coordinates


Entity_and_Attribute_Information:
Detailed_Description:
Entity_Type:
Entity_Type_Label: line[number].xyz
Entity_Type_Definition: digital surface elevation data
Entity_Type_Definition_Source: USGS
Attribute:
Attribute_Label: X
Attribute_Definition: Location X-coordinate of the data point.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 486997.617
Range_Domain_Maximum: 489962.263
Attribute_Units_of_Measure: meters
Attribute_Measurement_Resolution: 0.001
Attribute:
Attribute_Label: Y
Attribute_Definition: Location Y-coordinate of the data point.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 5381456.319
Range_Domain_Maximum: 5383932.558
Attribute_Units_of_Measure: meters
Attribute_Measurement_Resolution: 0.001
Attribute:
Attribute_Label: Z
Attribute_Definition: Location Z-coordinate of the data point.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: -10.00
Range_Domain_Maximum: 0.00
Attribute_Units_of_Measure: meters
Attribute_Measurement_Resolution: 0.01
Detailed_Description:
Entity_Type:
Entity_Type_Label: WESC[day]_[number].xy
Entity_Type_Definition: digital Acoustic Doppler Current Profiler data
Entity_Type_Definition_Source: USGS
Attribute:
Attribute_Label: X
Attribute_Definition: Location X-coordinate of the data point.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 486997.617
Range_Domain_Maximum: 489962.263
Attribute_Units_of_Measure: meters
Attribute_Measurement_Resolution: 0.001
Attribute:
Attribute_Label: Y
Attribute_Definition: Location Y-coordinate of the data point.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 5381456.319
Range_Domain_Maximum: 5383932.558
Attribute_Units_of_Measure: meters
Attribute_Measurement_Resolution: 0.001
Detailed_Description:
Entity_Type:
Entity_Type_Label: sediment grain size data
Entity_Type_Definition: surface elevation data
Entity_Type_Definition_Source: USGS
Attribute:
Attribute_Label: Lon
Attribute_Definition: Location X-coordinate of the data point.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: -123.58611
Range_Domain_Maximum: -123.13611
Attribute_Units_of_Measure: decimal degrees
Attribute_Measurement_Resolution: 0.00001
Attribute:
Attribute_Label: Lat
Attribute_Definition: Location Y-coordinate of the data point.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 48.58611
Range_Domain_Maximum: 48.60833
Attribute_Units_of_Measure: decimal degrees
Attribute_Measurement_Resolution: 0.00001
Attribute:
Attribute_Label: Depth_m
Attribute_Definition: Location Z-coordinate of the data point.
Attribute_Definition_Source: USGS
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Minimum: 0.00
Range_Domain_Maximum: 10.00
Attribute_Units_of_Measure: meters
Attribute_Measurement_Resolution: 0.01
Overview_Description:
Entity_and_Attribute_Overview:
Sample of digital surface elevation data XYZ ASCII file, bathy/line95.xyz:
X             Y              Z
487989.879521 5381998.198351 -3.31
487990.116289 5381998.892258 -3.34
487989.943243 5382001.029467 -3.40

Sample of Acoustic Doppler Current Profiler XY ASCII file, ADCP/RAW/WESC053107_010p.xy:
X                Y
487869.695129    5382286.342641
487870.234235    5382287.490111
487871.174033    5382288.284718

Sample of sediment sampling log:
Station Local_Time       UTC           Lon             Lat           Depth_m    Comment
1    6/1/07 20:44    6/2/07    3:44    -123.1430877    48.60642247    2.286     -
2    6/1/07 20:35    6/2/07    3:35    -123.1416559    48.60596625    2.1336    18.6 C
3    6/1/07 20:28    6/2/07    3:28    -123.1396819    48.60476647    2.4384    22.4 C
Entity_and_Attribute_Detail_Citation: none


Distribution_Information:
Distributor:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey, Coastal and Marine Geology
Contact_Person: Eric Grossman
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical address
Address: 400 Natural Bridges Dr
City: Santa Cruz
State_or_Province: CA
Postal_Code: 95060-5792
Country: USA
Contact_Voice_Telephone: (831) 427-4725
Contact_Facsimile_Telephone: (831) 427-4748
Contact_Electronic_Mail_Address: egrossman@usgs.gov
Distribution_Liability:
Although this data set has been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and/or related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials.

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.


Metadata_Reference_Information:
Metadata_Date: 20070917
Metadata_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey, Coastal and Marine Geology
Contact_Person: Eric Grossman
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical address
Address: 400 Natural Bridges Dr
City: Santa Cruz
State_or_Province: CA
Postal_Code: 95060-5792
Country: USA
Contact_Voice_Telephone: (831) 427-4725
Contact_Facsimile_Telephone: (831) 427-4748
Contact_Electronic_Mail_Address: egrossman@usgs.gov
Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998

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